1. Field of the Invention
This invention relates generally to remote instrumentation reading systems, and more particularly to an apparatus and method for automatically transmitting information by RF signals from a plurality of remote instrument reading units to a mobile collection center.
2. Description of the Prior Art
The need for automatically communicating from a plurality of instrumentation devices located at fairly remote and inaccessible locations, to a central collection center, has been acutely present for many years. This need is perhaps best exemplified in the use monitoring of "utility" commodities such as gas, water, electricity, and the like. The use of such utility commodities has traditionally been monitored by meters physically located at the situs of entry of such commodity into the user's facility or residence. It is hard to believe that in today's technologically advanced society with the ready availability of complex, relatively inexpensive electronic circuitry, that a ready practical solution to the automatic meter reading problem has not yet surfaced. The reality of the situation is, however, that the overwhelming majority of utility meter readings are still recorded by hand (i.e. by first-hand recording of the accumulated meter information by meter reading personnel, who generally travel on foot to locate and read the respective utility meters at a user's facility). It can readily be appreciated that such procedure is highly inefficient, susceptible to error and requires many employees and entails considerable expense.
Before proceeding with a description of the prior art and of this invention it will be helpful to define certain applicable terminology as used herein. When referring to instrumentation monitoring, and in particular with regard to meter reading the terms "remote" and "automatic" meter reading have acquired separate meanings as used in the art. As used herein, the term "remote" refers to that meter reading situation wherein a person and/or his associated meter reading apparatus is within the general vicinity of the meter, but not necessarily in actual view of the meter when the reading is taken. "Remote", therefore generally implies that a person is directly involved in the meter reading process. The term "automatic" is used herein to refer to that meter reading sitatuion wherein the meter is automatically read by instrumentation, independent of the need for human intervention. As will become apparent from a more detailed description herein, the invention applies equally well to "remote" and to "automatic" (i.e. "automatic/remote") instrumentation reading applications, as above defined. Care should also be taken to distinguish between use of the term "remote" as used to designate a mere location as spaced apart from another entity, and as used in the " remote instrument reading" sense as above defined.
It is desirable, therefore, to have such meters automatically read from a mobile collection unit or from a central station, in a manner that would eliminate the requirement for a meter reading pesonnel's entry onto a user's premises. Such automatic/remote meter reading method and apparatus must be highly reliable and accurate, and above all, relatively inexpensive to install and compatible for retrofitting the large number of meters of varied construction already in operation in the marketplace. Numerous solutions of varying scope and complexity have been proposed for automating in whole or in part the meter reading process. However, for many reasons, including complexity, high cost, servicability impracticality for the general small-user accounts, low reliability, and the like, none of the techniques proposed in the art has yet provided a ready solution to the automation of meter reading.
Most automatic/remote meter systems of the past are similar in design in that they generally include an encoder device attached to the meter to provide an indication of the meter reading, means for storing the accumulated meter reading and a communication link for transmitting the stored information to a central collection station, typically when interrogated by the central collection station. Numerous encoder devices for such systems have been developed, ranging from simple magnetic, optical or capacitive switching elements, to more complex cam activated or electronic switching networks. Similarly, numerous communication links for such systems have appeared in the art. Such communication links have typically used telephone lines, power transmission lines of Radio Frequency (RF) signals for transferring data and/or control information between the remote meter reading units and the central collection station. Each of such techniques has had problems or shortcomings in attempting to provide a practical and effective solution to the automatic/remote meter reading problem.
Those communication links using the telephone lines of the subscriber/commodity user, enable relatively detailed communication between a central collection station and the remotely located meter units, but are limited in the use flexibility of such systems. Further, the installation of such automatic systems requires an undesirable connection of the meter reading apparatus to the user's telephone system. The retrofitting of such systems is generally complex and expensive and is justified primarily only for use with larger commercial accounts. Similarly, those automatic systems which employ the user's power lines as the communication link suffer from the same limited flexibility and installation disadvantages as those which employ the user's telephone lines. Both of the above systems depend upon a secondary hardwired transmission medium which is primarily configured and designed to carry information other than the accumulated data of the meter reading units.
A more practical solution appears to be provided by those automated meter reading systems that employ an RF communication link between the remote meter units and the central collection station. Such systems do not inherently suffer those retrofitting disadvantages associated with incorporating a telephone or power line communication link into the automated system. With an RF communication link system, the central collection station can be made mobile, by placing it in a mobile unit such as a van or the like, which can travel over any desired route in a community for collecting the information from remote meter reading units installed in facilities along that route. Typically, the mobile collection station transmits interrogating enabling signals to the instrument monitoring units, which in turn send RF reply signals back to the mobile collection unit, in the form of an identifier code of the respective remote meter reading unit, along with its encoded information and data. The mobile collection unit processes the received RF information for subsequent billing and repair or maintenance purposes. Typical examples of such RF communication link systems are illustrated is U.S. Pat. Nos. 3,705,385 and 4,031,513. In theory, such remote meter reading structures which employ RF communication principles are simple to retrofit to existing meter installations, require no external connections to either telephone or power lines, and can be structured in self-contained manner to operate from their own battery sources.
While conceptually offering significant advantages over their telephone or power line communication link counterparts, the RF communication link remote meter reading systems of the prior art have not yet been configured in a manner so as to take full advantage of their unique status. A primary reason for the limited success of the RF communication link system to date has been the relatively high cost of the remote meter reading units, as dictated by the circuitry required therein for processing the enable polling signal received from the mobile collection unit. Prior art RF communication link techniques for remote meter reading applications have generally used remote unit polling schemes whereby the mobile collection unit transmits unique remote unit identifier codes in a manner so as to activate or enable for transmission, only one remote meter reading unit at a time. Such schemes necessarily require the remote units to have relatively expensive or complex decoding and comparator circuitry for identifying the polling signal which is unique to that particular remote unit. An alternate approach that has been employed in the art has been to activate more than one meter reading unit at a time, which simultaneously activated remote units have been pretuned for transmitting at identifiably different RF frequencies. Such technique, while requiring less expensive enable decoding circuitry requires generally expensive and accurately tuned circuits in the remote units (due to the relatively narrow frequency range in which such units are permitted to operate), thereby increasing the manufacturing costs of the remote units. Further, the use-flexibility of the remote units of such systems is reduced in that care in installation of such units must be maintained so as not to install two similarily tuned units within an RF interference range of one another. Various other techniques using RF link communication principles have been developed in the art, but have generally suffered from similar low use-flexibility or relatively high remote unit cost disadvantages. Another drawback of such prior art RF communication link systems has been the high power consumption required by the remote units, significantly reducing their battery life, and making systems using such units impractical for extended life, low maintenance applications. Such prior art systems typically require battery replacement at unacceptable, two month intervals.
Therefore, while many automatic/remote instrumentation reading systems have been developed in the art, which utilize one or more of the various communication link techniques generally described above, no one automatic remote instrumentation reading system has yet been designed which affords the capabilities of automatic mass instrumentation data accumulation from, for example, consumer's facilities, which meets the universal needs of utility companies. The present invention addresses the shortcomings of prior art automatic instrumentation reading and transmitting systems. While the invention applies generally to the collection and transmission of data from any type of remotely located instrumentation units, for ease of description, further reference herein will only be made to its applicability to meter reading systems, it being understood that the principles of this invention can be applied more broadly to instrumentation in general. The automatic/remote instrument reading system of this invention provides accurate and reliable transmission of, for example, encoded meter information that can be readily identifiably associated with the remote meter from which such information was transmitted. The automatic/remote instrument reading system of this invention employs a unique remote instrument reading method and associated apparatus that permits a large plurality of remote data collecting instruments to simultaneously transmit their respective encoded data to a mobile collection unit. The instrument monitoring transponder units themselves are relatively inexpensive in that no special or unique polling/decoding circuitry or highly tuned RF circuitry is required. The transmission units are easy to install in existing instrumentation and flexible for use, for example, with virtually any known meter structures. Their unique design provides for high reliability and a small battery with long battery life, typically in excess of five years, with minimal maintenance or servicing. These and other benefits and advantages of the automatic/remote instrumentation reading system method and apparatus of this invention will become apparent from a more detailed description of the invention.